Ellipsograph



(Model.)

H. R. ooR-KHILL, Jr.

BLLIPSOGRAPH.

No'.l 492,142.

we @zfmdw @y l I I I x l l l;

Patented Feb.2l, `1893.

No Q u N TH: unwms PETERS cu, Pnomuruo.. wAsHmsYoN. n c.

STATES r Urirrn Arai einen.

lELLlPsoeRAPH.

SPECIFICATION forming part of Letters Patent No. 492,142, dated February21, 1893.

Application tiled March 26,1892. Serial No. 426,569. (Model.)

T0 all whom it may concern:

Be it known that I, HENRYYR. CORKHILL, J r., of Rochester, in the countyof Monroe and State of New York, have invented a new and usefulImprovement in Ellipsographs, which improvement is fully set forth inthe following specification and shown in the *accompanying drawings.

The object of my invention is to producea device for conveniently andaccurately tracing ellipses, which possesses certain advantages oversimilar devices heretofore used, the invention being hereinafter fullydescribed and particularly pointed out in the claims.

Referring to the drawings Figure l is a plan of my improvedellipsograph, parts being broken away and other parts shown in variouspositions by full and dotted lines. Fig. 2 is a side elevation of thedevice seen as indicated by arrow 2 in Fig. 1. Fig. 3 is a centrallongitudinal section taken on the dotted line 3 3 in Fig. l. Fig. Il isan end elevation seen as indicated by arrow 4 in Fig. l. Fig. 5 is aplan of some of the interior parts. Fig. 6 is a cross section of thetracing arm taken on the dotted line 6 6 in Fig. 1. Fig. 7 is a plan ofa crank-arm pin with adjacent parts.

Referring to the parts shown A is the base or body of the instrument,which is hollow and preferably made of cast met-al, and B the tracingarm carrying a tracing point d. The.

base piece is formed with four vertical standards b arranged in acentral longitudinal line, the three at the left being equal in height,and having Within them shafts c c c', as shown in Figs. 2 and 3. At theupper ends of these shafts are rigidly secured similar horizontalcrank-arms d d d which turn with the shafts and bear upon the upper endsof the standards. Within the base are two cranks e e each securedrigidly to a shaft c, and a crank gear f secured to the shaft c.

g is a rod connecting the three cranks, being held by crank pins h h h,one secured rigidly in each of the two cranks and in the gear.

Within the right-hand short standard b is fitted a vertical shaft isimilar to the shaft c, to the lower end of which, and Within thebase-piece, is secured a spur gear 7c similar to, and engaging, the gearf. At the upper end of the shaft 'L' is secured an operatingcrank Z bymeans of which all the shafts c c c and t',

and the crank-arms d d d are caused to revolve. The crank-arms d d d arearranged so that all three will be exactly in line when turnedlongitudinally overa-the base piece, or vparallel when turned atright-angles to the base piece, as shown in Fig. l. The connecting rod gserves to keep thefarms all thus relatively arranged. These arms carryand operate the tracing arm B.

The crank-arms are, as a matter of convenience, made T-shape in crosssection, as

shown, and are provided with adjustable crank-pins n n n having lips oturned horizontally under the projecting edges of the arms. Thecrank-pins are provided with vertical clamping screws r r r threaded inthe reduced parts p, having their points hearing upon the respectivecrank-arms, by means of which the crank-pins are held to place on thecrank-arms.

Upon the two crank-pins n n is mounted a holding-bar or body s forholding the tracing arm B. This tracing arm is formed with a centrallongitudinal slot t,Fig. 1, occupied by the bar s, the two sides of thearm occupying horizontal grooves or rests in the opposite edges of theholding-bar, as shown iu Fig. 6. The holding-bar is provided with acap-piece u above the tracing arm, held to place by fastening screws fu.The parts are fitted so that the tracing arm may slide freely butwithout lost motion in a longitudinal direction in its bearings in theholding bar.

w are Washers resting upon the cap-piece u, rigid with the crank-pinsnn, so as to turn with the latter when the crank-arms d are revolved.The crank-pins pass through vertical circular openings in theholding-bar, as shown in Fig. 3, which constitute the vertical bearingsbetween the pins and the bar. For horizontal bearings the holding barrests upon the upper horizontal faces of the crankpins. As constructed,when the crank-arms d cl arev revolved the crank-pinsnn, the wash-V ersw w and the clamping screws r r all turn together, the crank-pins nturning in their bearings, in the holding-bar. l

The crank-pin fn', is provided with a prismatic block Figs. l and 3,which occupies a transverse slot y in the tracing arm B. This block isformed with a tonguez fitted to a corresponding horizontal groove aformed in the tracing arm. Then the crank-arms are revolved thecrank-pin a turns in the block fc for a bearing similar to the manner inwhich the crank-pins n n turn in the holding-bar s. The tongue z,fitting closely in the groove a, tends to keep the tracing arm steadyand prevents it from rocking upon its bearings in theholding-bars. Theslots t and y in the tracing arm are at right-angles with each other,and disconnected, the slot j1/, being beyond the rear end of the slot t.

The tracing arm B is divided, as shown in Fig. 2, the parts being'fittedto turn upon each other as with a swivel movement, held togetherby a clamping pivot-screw Z1.

The three crank-pins n n. ot are shown placed centrally over therespective shafts c c c, the axes of the cl`amp-screws fr r o"coinciding with the axes of the shafts. In this position a revolution ofthe crank Z and crankarms (Z CZ CZ', would cause no motion of thetracing point a.

To cause the tracing point to describe a figure the crank-pins must bemoved away from the shafts, each along its crank arm (Z. By moving thepins n nl, with the holding bar, toward the outer ends of the crank-armsthe vertical dimension l I of the figure, C, will be determined; and avsimilar movement of the crank-pin n' will determine the horizontaldiameter 2 2 of the figure. It' all three of the crank-pins are movedequally distant from their respective centers of motion, that is to saythe shafts c c c', the ligure C will be a circle. If an ellipse is to bedescribed having its major axis horizontal or parallel with the tracingarm, the crank-pin n will be moved farther from its center of motionthan the crank-pins 'a n are from theirs. If the major axis of theellipse is to be vertical or at right angles with the tracing arm, thecrank-pin n must be nearer its shaft c than the other two crank pins nn, are to their respective shafts c c. The crank-arms (Z rZ carry theholdingbar around in a circle, and the crank-arm d carries the block .0cin a circle when the operating crank Z is turned. If the pins n n occupycentral positions over their respective shafts c c, as shown in fulllines in Fig. I, and the pin n is moved away from its shaft the tracingpoint will, when the crank Z is turned, describe a straight line 2 2,having a length equal to twice the distance said pin fa is moved fromthe shaft c. If, new, the pins n n be moved successively away from theirshafts through small distances and a figure be described by the tracingpoint each time, a series of ellipses will be formed having the line 2 2for a common major axis, until the distance of said pins lfrom theirrespective shafts becomes equal to the distance the pin n is from itsshaft, when the figure will be a circle with the line 2 2 fora diameter.And, conversely, if the pins n n. are placed away from the shafts c cand the pin n remains over its shaft a revolution of the crank Z willcause the tracing point to describe a straight line corresponding to ll, at right angles with the axis of the tracing arm. Then, by moving thepin n successively through small distances as in the first case, untilits distance from the shaft c equals the distance of a pin n from itsshaft c, a series of ellipses may be drawn having line l I for a commonmajor axis, the last figure being a circle with said line l l for itsdiameter.

The edges of the arms CZ (Z are divided into equal scales of equalparts, as shown in Fig. 4, the division marks of which may, ifnecessary, be carried over upon the upper surfaces of the arms, as shownin Fig. l. By this means the crank-pins n n may be set at any givendistance, within limits, from their centers of motion, this distancecorresponding to the semi-major axis or semi-minor axis as the case maybe, of the ellipse to be drawn. The division marks on these two arms d.(Z are alternated, as will be understood by comparing the marks on thearm CZ, Fig. 4, with the marks on the fictitious scale c whichrepresents the `other arm (Z. If the scales on the two arms Vshowsubdivisions of an inch, as eighths and sixteenths, for example, then byalternating }the two scales, as shown, so that the marks in idicatingeighths on one arm shall bisect the `spaces on the other the pins n nmay be set to thirty-seconds of an inch without such line division beingmade on the scale of either arm. In a similar manner the two sides ofIthe transverse slot y in the tracing arm are jdivided into alternatedscales, as shown, by means of which the block t may be exactly set asuse of the instrument may require.

In setting the crank-pins n n to describe a figure the crank arms arefirst turned inline under the tracing arm and the clamp-screws r o areloosened. The pins fn n (with the holding-bar) are then moved to theirproper positions upon the arms, reference being had to the scales, afterwhich the clamp-screws r r are set up firmly. Then turning the armsacross the device and at right angles thereto, as shown in Fig. l, theclamp-screw r is loosened and the pin n moved to bring the block a: toits proper place in the slot y indicated by the scale on the tracingarm, the screw r beingthen firmly set.

As shown in Fie. 4, the forward crank-pin n is beveled down to an edge,o', adjacent to the scale on the arm CZ to facilitate the setting ofsaid pin to the proper place on the scale. The other crank-pin n issimilarly formed, and for the same purpose.

To determine when the crankarms are exactly in line under the tracingarm for the purpose of setting the pins n n, as above described, Iprovide a centering pin or detentf, Figs. 2 and 3, held by thebase-piece Ain position to have its point enter a hole gin the gearf,Figs. l and 5. A similar hole is formed in the gear ninety degrees fromthe hole g so that when the gear is turned to receive the pin in thissecond hole the arm zZ will stand parallel with the slot y, in whichposition of IOO IIO

the parts the pin n may be shifted and set as described.

Stop-screws h', Figs. 1 and 2, are inserted in the respective arms d dd', forming stops for the respective pins n n n. These stopscrews are soplaced that when said pins are moved against them the vertical axes ofthe pins will correspond with the axes of the respective shaft c c c.When the pins are in these positions a revolution of the operating crankl will cause no motion to the tracing point, as above stated.

To form the slot y in the tracing arm I commonly use a rear bar t" andtwo equal parallel spacing blocks 7c k', held together by fasteningscrews Z as shown in Figs. l and 4. This slot may, however, ifdesirable, be formed in the arm like the slot t, without surroundingpieces. Also in constructing this instrument the gears 7c and f maybedispensed with if found desirable and replaced by simple cranks likethose referred to by e e, the connecting rod g being extended to connectall. In this case the hole g for the detent pin f would be formed in therod g, and some simple provision made for holding the arm d', under theslot y, not involving invention.

In constructing this ellipsograph the edges t t of the base-piece A aremade straight and parallel so that the instrument may be used againstthe edge of the blade of a T-square, or other straight edge.

On account ofthe swivel joint in the tracing arm the tracing point maybe turned aside or offset, as shown in Fig. l, and ceased to draw afigure out of line with the axis of the instrument.

It is frequently necessary for a draftsman to describe a semi-ellipse,as in drawing an arch, or a fourth of an ellipse, as when representingthe overhanging portion of a projecting beam. To facilitate theexecution of such figures or portions of lan ellipse Iprovide a disk ordial p', Figs. 1 and 2, under the operating crank Z and securely seated.on the standard h of the base A. This dial is marked with four equallyspaced peripheral marks s', and the crank is provided with a pointer r2in position to traverse the periphery of the dial and pass these markswhen said crank is turned. By means of this dial vand the pointer anexact fourth of an ellipse as from l to 2, or a semi-ellipse as from laround to l or from 2 around `to 2, may be drawn.

What I claim as my invention is- 1. An ellipsograph formed with abasepiece, a pair of revolving crank-arms held by said base piece, a holdingbar mounted upon said crank-arms, and a tracing arm held by saidcrank-arms and provided with a tracing point overhanging said basepiece, in combination With a third crank-arm held by said base piece inposition to bear against said tracing armv and adapted to move itlongitudinally in the holding bar, substantially as shown and described.

2. An ellipsograph having a tracing arm carrying a tracing point, and aholding bar or holder formed with rests to receive th-'tracing arm, incombination with revolving crankarms for carrying the holding-bararound, and a revolving crank-arm adapted to act alternately in oppositedirections upon the tracing arm to reciprocate the lat-terlongitudinally in its bearings in the holding-bar, the tracing arm beingformed in two parts and united bya swivel joint and a fastener for theVating crank to turn the crank-arms, substantially as described.

4. An ellipsograph having, in combination, a tracing arm, arevolvingholder for the tracing-arm, revolving crank-arms for carrying theholding-bar, adjustable crank-pins on the crank-arms,`and clampingscrews for thev crank-pins, the crank-arms being provided with scales ofequal parts for setting the crankpins, substantially as shown anddescribed.

5. The combination in an ellipsograph of a tracing arm, a revolvingholding-bar for the tracing-arm, revolving crank-arms for carrying theholding-bar, adjustable crank-pins on the crank-arms, and clampingscrews for the crank-pins, each of said crank-arms being provided with ascale of equal parts, alternated with each other, substantially as andfor the purpose set forth.

6. An ellipsograph-having atracing arm, in combination with a holder forthe tracing arm, a pair of revolving crank-arms for carrying theholding-bar, and a crank-arm to move the tracing-arm longitudinally,adjustable crankpins on the several crank-arms and clamping screws forsaid crank-pins, and stops on said crank-arms to limit the motion of thecrankpins upon the crank-arms, substantially as and for the purposespecified.

7. The combination in an ellipsograph, of a tracing arm, a revolvingholder for the tracing arm, a series of crank-arms to operate thetracing arm, an operating-crank to revolve the crank-arms, a disk ordial associated with the operating crank, and a pointer for the dialattached to the operating crank, substantially as shown and described.

8. In combination with the tracing arm of an ellipsograph, a revolvingholder for the tracing arm, a series of crank-arms for operating thetracing arm, an actuator for the crank-arms, and a detent to hold thecrankarms in position, substantially as shown and for the purposespeciiied.

9. An ellipsograph having a hollow base IIO formed with aseries ofvertical standards projeeting therefrom, in combination with verticalshafts in said standards, cranks secured to Jbhe shafts Within the base,a connecting rod joining` said cranks, crank-arms secured to the shaftsabove the standards, and a trac ing arm held and operated by thecranlearms, and 1n eans to revolve the shafts, substantially as shownand described.

lO. An ellipsograph having a tracing arm and a holder for the tracing.,rarm,in combination with a pair of revolving crank-arms for carrying theholder for the tracing arm, a crank-arm to move the tracing,r arnilongitudinally, a crank-pin on said last named crank arm, and a slidingblock on the crank-pin to press the tracing' arni, thelatterbeingformedwith a groove or race and the sliding block having a tongue to entersaid groove, as and for the purpose specified.

ll. The combination in an ellipsograph of a tracing arm, a revolving`holder for the traeing arm, a series of crank-arms for operating thetracingT arm, an adjustable crank-pin for each crank-arm, andela1npscrews for the crank-pins, the latter being formed with lipsturned under projecting parts of the respective erank-arms,substantially as shown.

In Witness whereof I have hereunto set my hand, this 21st day of March,1892, in the presence of two subscribing Witnesses.

HENRY R. CORKHILL, JR.

lVitnesses:

ENOS 13. WHITMORE, M. L. MCDERMOTT.

